Development of a Prototype Cavity Beam Position Monitor for the Compact Linear Collider

Frankie Cullinan

Research output: ThesisDoctoral Thesis

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The Compact Linear Collider (CLIC) is a proposed electron positron collider
with a maximum centre of mass energy of 3 TeV. In order for it to operate at its
maximum luminosity, precise alignment of the accelerator elements in the main
linac and beam delivery system is required. The beam based alignment algorithm designed to do this requires measurements of the transverse beam position with a resolution of 50 nm and multiple position measurements within a single 156 ns long bunch train. The proposed solution is a cavity beam position monitor (BPM) with a low quality factor. A prototype cavity BPM pick-up has been designed and manufactured for tests on the probe beamline of the third CLIC test facility (CTF3) at the European Organisation for Nuclear Research (CERN). This thesis presents the measurements performed on this prototype in the laboratory, the development of the associated processing electronics and tests with beam.
The resonant frequencies and quality factors of the modes of interest in the
two cavities of the prototype BPM pick-up were measured in the laboratory
using a network analyser. Problems with the design of the pick-up geometry are
identified and solutions proposed. Analytical expressions for the amplitude and
phase and total energy of the multiple bunch signals are derived and a processing algorithm for the deconvolution of the single bunch waveform from the multiple bunch signal is presented. A set of receiver electronics for analogue processing of the microwave frequency signals has been designed and built from connectorised components. Beam-based measurements of the sensitivity of the position cavity signal to beam position and the reference cavity signal to charge have been made.
The cavity BPM has been calibrated and used to measure the beam position jitter
at the BPM location. Finally, the performance of the whole system is discussed
and possible tests that could be used to determine the measurement bandwidth
of the cavity BPM are proposed.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Boogert, Stewart , Supervisor
Award date1 Nov 2014
Publication statusUnpublished - 2014

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